Subterranean formations surrounding oil wells, gas wells, water wells and other similar bore holes, are frequently treated with particulate material such as sand which has been coated with a curable phenolic resin. The type of treatments vary but can include hydraulic fracturing, sand consolidation, and gravel pack completion. In these treatments the coated particulate material is injected into the well and into the geological formation surrounding the bore hole. The curable phenolic resin coating on the particulate material is cured in the formation to bond the particulate material together. This gives a permeable filter which prevents small sand particles and other finely divided material from blocking the perforations in the well casings and from damaging the pumping and other handling equipment.
Occasionally an excess of the resin coated particulate material is pumped down into the well and fills the wellbore above the perforations in the well casing. If the resin coating on the particulate material cures within the wellbore, it firms a consolidated mass which drastically impedes the flow of liquid from the well. When the occurs, it is often necessary to employ a special boring rig to remove the consolidated material to obtain satisfactory production from the well. Such a procedure is both time-consuming and expensive.
We have now discovered that certain solvents will break up the consolidated material permitting its removal from the wellbore without the need to resort to the costly boring procedure.